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From:   Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To:     linux-kernel@vger.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        stable@vger.kernel.org, Jon Maloy <jmaloy@redhat.com>,
        Hoang Le <hoang.h.le@dektech.com.au>,
        "David S. Miller" <davem@davemloft.net>,
        Sasha Levin <sashal@kernel.org>
Subject: [PATCH 5.12 080/161] tipc: fix unique bearer names sanity check
Date:   Tue,  8 Jun 2021 20:26:50 +0200
Message-Id: <20210608175948.147832149@linuxfoundation.org>
In-Reply-To: <20210608175945.476074951@linuxfoundation.org>
References: <20210608175945.476074951@linuxfoundation.org>
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From: Hoang Le <hoang.h.le@dektech.com.au>

[ Upstream commit f20a46c3044c3f75232b3d0e2d09af9b25efaf45 ]

When enabling a bearer by name, we don't sanity check its name with
higher slot in bearer list. This may have the effect that the name
of an already enabled bearer bypasses the check.

To fix the above issue, we just perform an extra checking with all
existing bearers.

Fixes: cb30a63384bc9 ("tipc: refactor function tipc_enable_bearer()")
Cc: stable@vger.kernel.org
Acked-by: Jon Maloy <jmaloy@redhat.com>
Signed-off-by: Hoang Le <hoang.h.le@dektech.com.au>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 net/tipc/bearer.c | 46 +++++++++++++++++++++++++++-------------------
 1 file changed, 27 insertions(+), 19 deletions(-)

diff --git a/net/tipc/bearer.c b/net/tipc/bearer.c
index 1090f21fcfac..0c8882052ba0 100644
--- a/net/tipc/bearer.c
+++ b/net/tipc/bearer.c
@@ -255,6 +255,7 @@ static int tipc_enable_bearer(struct net *net, const char *name,
 	int bearer_id = 0;
 	int res = -EINVAL;
 	char *errstr = "";
+	u32 i;
 
 	if (!bearer_name_validate(name, &b_names)) {
 		errstr = "illegal name";
@@ -279,31 +280,38 @@ static int tipc_enable_bearer(struct net *net, const char *name,
 		prio = m->priority;
 
 	/* Check new bearer vs existing ones and find free bearer id if any */
-	while (bearer_id < MAX_BEARERS) {
-		b = rtnl_dereference(tn->bearer_list[bearer_id]);
-		if (!b)
-			break;
+	bearer_id = MAX_BEARERS;
+	i = MAX_BEARERS;
+	while (i-- != 0) {
+		b = rtnl_dereference(tn->bearer_list[i]);
+		if (!b) {
+			bearer_id = i;
+			continue;
+		}
 		if (!strcmp(name, b->name)) {
 			errstr = "already enabled";
 			NL_SET_ERR_MSG(extack, "Already enabled");
 			goto rejected;
 		}
-		bearer_id++;
-		if (b->priority != prio)
-			continue;
-		if (++with_this_prio <= 2)
-			continue;
-		pr_warn("Bearer <%s>: already 2 bearers with priority %u\n",
-			name, prio);
-		if (prio == TIPC_MIN_LINK_PRI) {
-			errstr = "cannot adjust to lower";
-			NL_SET_ERR_MSG(extack, "Cannot adjust to lower");
-			goto rejected;
+
+		if (b->priority == prio &&
+		    (++with_this_prio > 2)) {
+			pr_warn("Bearer <%s>: already 2 bearers with priority %u\n",
+				name, prio);
+
+			if (prio == TIPC_MIN_LINK_PRI) {
+				errstr = "cannot adjust to lower";
+				NL_SET_ERR_MSG(extack, "Cannot adjust to lower");
+				goto rejected;
+			}
+
+			pr_warn("Bearer <%s>: trying with adjusted priority\n",
+				name);
+			prio--;
+			bearer_id = MAX_BEARERS;
+			i = MAX_BEARERS;
+			with_this_prio = 1;
 		}
-		pr_warn("Bearer <%s>: trying with adjusted priority\n", name);
-		prio--;
-		bearer_id = 0;
-		with_this_prio = 1;
 	}
 
 	if (bearer_id >= MAX_BEARERS) {
-- 
2.30.2